Control apparatus for aircraft



R. J. KUTzLER 2,634,925

CONTROL APPARATUS FOR AIRCRAFT Filed March l5, 1948 2 SHEETS--SHEET l (Ittorneg April 14, 1953 R, J KUTZLER 2,634,925

CONTROL APPARATUS FOR AIRCRAFT Gttorneg Patented Apr. 14, 1953 CONTROL APPARATUS FOR AIRCRAFT Robert J. Kutzler, Minneapolis, Minn., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application March 13, 1948, Serial No. 14,787

18 Claims. l

This invention pertains to flight control apparatus for an aircraft. An embodiment of the invention as illustrated has been applied to the control of an aircraft of the flying wing type. Although adapted in its preferred form to the control of an aircraft of the flying wing type, the invention nevertheless may be applied to other types of aircraft.

The fiying wing as its name implies is a form of aircraft which is comprised principally of a wing section and does not have the extended fuselage and tail section as in the conventional types of aircraft.

Control of the flying Wing about the vertical axis is obtained by means of two rudders. A rudder is placed at the extremity of each wing at the trailing edge thereof. The rudders are separately operated to increase the drag in the portion of the wing in which they are mounted and the increased drag on the wing having the operated rudder serves to give control about the turn axis of the plane. Control of the flying wing about the roll and pitch axes is obtained by control surfaces called elevons. One elevon is mounted in each wing inboard of the rudder and in the trailing edge of the wing. The elevons are operated at times in the same direction to give the conventional elevator action to the aircraft. On other occasions the elevons may be operated in opposite directions to apply the aileron action to the aircraft. Means have been provided foroperating the rudders and elevons.

The flying wing in the embodiment of my invention illustrated is stabilized about its turn, roll, and pitch axes by a directional gyroscope and a vertical gyroscope. The directional gyroscope stabilizes the aircraft about the turn axis vby applying rudder movement only for small deviations. For large deviations about the turn axis the directional gyroscope applies aileron as well as rudder corrections.

The directional gyro stabilizes the aircraft about the turn axis, as stated, and therefore stabilizes the heading of the aircraft. In general the heading of the aircraft is the same as the direction in which the aircraft is moving relative to its surrounding air or supporting medium. However, under certain conditions the aircraft may be moving in a different direction relative to the air from that in which its longitudinal axis is headed. Under such conditions the aircraft is in yaw or is said to be yawed. As long as the heading is maintained constant, the directional gyroscope which stabilizes the craft on a heading will not sense any difference between the heading of the aircraft and the direction in which it is moving. Means have been provided that senses when the aircraft is not heading in the direction in which it is moving. This means for sensing differences between the heading and the direction in which the aircraft is going is also utilized to apply corrective movement to the rudders of the aircraft whereby the aircraft is forced to head in the direction in which it is moving. Any resulting attempt to compel the aircraft to change heading and to head in the direction in which it is going to thereby remove yaw will also cause a corrective movement to be applied to the rudder from the directional gyro. Since the correction from the directional gyro due to change of heading resulting from correction of yaw and applied to the rudders would be opposed to that applied by the means for sensing the difference between the heading and the direction in which the aircraft is going, it is an object of this invention to provide the yaw sensing means with an arrangement for overriding any control exerted by the directional gyro on the rudders in response to such change in heading.

Since the overriding feature of the yaw control has through the rudders compelled the aircraft to change its heading, means have been provided whereby the directional gyro responding to the change in heading effects operation of the ailerons to bank the aircraft causing it to turn and to restore the aircraft to its original heading.

Many aircraft have a tendency to assume the yawed condition in flight that is a condition in which they are not headed in the direction in which they are moving due to some inherent structural condition of the aircraft. The yawed condition of the aircraft may be corrected by operating one or the other rudders to cause the aircraft to head in the direction in which it is' going. Since such movement or displacement of the rudder must necessarily be permanent if the yawed condition is to be permanently corrected it is desirable that some means be provided for maintaining a rudder in a displaced position from its normal position.

A further object therefore of this invention is to provide means for sensing when yaw exists in the flight of the aircraft and to provide a permanent displacement of the rudder to permanently correct for the yawed condition.

Another condition arising during the flight of an aircraft which requires a permanent displacement ofthe control surfaces of the aircraft is known as unsymmetrical power. Unsymmetrical power occurs in multi-engine aircraft when the motors on one side of the longitudinal axis of the aircraft differ in power output from those motors on the other side of the longitudinal axis of the aircraft. When the power output of the motors on opposite sides of the longitudinal axis is not the same, the aircraft will tend to turn tov/ard the side having the least power. The presence of unsymmetrical power not only causes the aircraft to turn toward the side having the lesser power, but the wing on the side of less power also begins to drop. The dropping of the wing results from the loss in lifting power of the wing. The lifting power decreases probably because the speed of the air over the wing which is aided by the propeller slip stream decreases on power change of motors. Since the condition of unsymmetrical power requires not only a correction for the tendency of the aircraft to turn about the vertical axis and also for a tilting of the wing about the longitudinal or roll axis, means have been provided to apply permanent corrections for these conditions.

The condition of unsymmetrical power manifests itself at the outset by a veering of the aircraft about the turn axis. Such veering or change in heading will be sensed by the directional gyro which effects operation of the rudder to check such change in heading. Since it is desired to anticipate any movement of the aircraft about the roll axis, means have been provided whereby a signal from the directional gyro causes the operation of the aileron operating means to apply proper aileron to anticipate any change in the lateral attitude of the aircraft. Since the means for preventing changes in lateral attitude or tilting of the aircraft about the roll axis must provide in this instance a permanent correction, it is a further object of this invention to provide means for applying a permanent displacement of the ailerons of the aircraft to compensate for any tendency to alter the lateral attitude of the aircraft.

Correction for the existence of unsymmetrical power requires not only a permanent displacement of the ailerons but also requires a permanent displacement of a rudder on the aircraft. Anticipating corrections for tilt about the roll axis have been generally described as being controlled by the directional gyro. It would appear that even with the tilt about the roll axis of the aircraft corrected that the aircraft nevertheless would have a tendency to turn about the turn axis owing to unsymmetrical power. Where the aircraft is turning as stated due to unsymmetrical power but retains its lateral attitude in fiight, the aircraft may skid due to the centrifugal eifect of the turning action. However, when the aircraft skids, it is in a condition of yaw; and the presence of yaw is immediately detected by the yaw sensing means. The yaw sensing means eects the operation of the rudders to correct for any yawed condition. In the means employed, the yawed condition is corrected by a permanent displacement of the rudder so that the condition for unsymmetrical power is corrected by a permanent displacement of the rudder as well as the ailerons. The directional gyro also senses turning from the desired heading and applies corrective rudder movement.

The aircraft is provided as stated with apparatus for stabilizing it about the turn, roll, and pitch axes. In addition to automatic stabilization, means have been provided whereby the aircraft may be manually controlled about the turn and roll axes through the operating means which position the control surfaces. The operating means for the control surfaces may therefore be controlled through the automatic stabilizing devices or by manually operated devices.

Another object of thisinvention is to provide resetting devices for the means which apply permanent compensating correction to the turn axis control surface and to the roll axis control surface. These resetting devices are selectively operable so thatif the cause of a condition is removed the control surfaces may be returned to a normal position.

Further objects of the invention may be ascertained by reference to a detailed description of the invention and the drawing showing a pre-Y ferred embodiment thereof wherein:

Figures 1A and 1B show a schematic arrangement of apparatus for controlling an aircraft in night.

Turn amis control Y As stated previously turn axis control of the iiying wing about the turn axis is obtained by two so-called rudders (not shown) which are mounted in the extremities of the wings. One rudder is provided near each tip of the wing. The function of each rudder is merely to increase the frontal resistance of the portion of the wing in which it is mounted. For this reason each rudder may consist of two vanes which may be projected one above and one below the surface of the wing perpendicular to the air stream to thereby increase the drag of such wing in flight. In the apparatus to be described, arrangements have been provided whereby only one rudder is in operated position at one time.

Considering the operating means for each rudder, the left rudder is actuated by cables l0 extending from a cable drum il. The cable drum il is driven by a rudder servomotor I2. The servomotor l2 is reversibly controlled by a left servomotor amplier i3. The amplifier i3 is supplied with an input control signal obtained from an input circuit which includes active components comprising a servo-balance and aligning network 22, a vertical gyro rudder network 44, a rate gyro and aligning network 51%, a yaw rudder bridge lil, a turn control network istil, and a directional gyro rudder and centering bridge ll).

The right rudder is connected to cables lll extending from a cable drum H2 which in turn is driven by a right rudder servomtor H3. The right rudder servomotor is reversibly controlled by the right servomotor amplifier Il. The right rudder servomotor amplifier is supplied with a control signal from a network which includes active components comprising a right rudder servobalanoe and aligning network 89, the vertical gyro rudder network Gli, the rate gyro and aligning network EG, the yaw rudder bridge le, the rudder turn control network li, and the directional gyro rudder and centering bridge |60.

The servomotor i2 and the amplifier I3 which reversibly controls its direction may be of the type disclosed in application 447,989 filed June 22, 1942 or that disclosed in U. S. Patent 2,425,733 issued August 19, 1947. As disclosed in the aforesaid application the amplier i3 may reversibly control the motor l2. The direction of rotation of the servomotor i2 depends upon the phase relationship between the voltage applied to signal input terminals i3, Il of amplifier i3 and that across the terminals i9 and 20 connected to a source of alternating voltage which may be the inverter, not shown, of the aircraft.` The right rudder servomotor |13 and its amplifier |14 are similar' to that .provided for the left rudder.

The left rudder servo-balance and aligning network 22 comprises a servo-balance and aligning bridge 24. The bridge 24 comprises a servobalance potentiometer 25 having a wiper 21 and a resistor 20. The resistor 26 forms two arms of the bridge 24 and it is connected across the ends of a secondary winding 26 of a transformer having a primary winding 30. The wiper 2l is operatively connected to the servomotor l2. The opposite two arms of the bridge 24 comprise an aligning potentiometer 3| having a resistor 32 and a wiper 33. connected across the ends of secondary winding 28 and parallel to the resistor 2E of potentiometer 25. The aligning wiper 33 may be positioned by a manual control knob 34. The network 22 also includes a rudder ratio or voltage dividing potentiometer 31 having a resistor 38 and a wiper 39. rEhe resistor 38 is connected across the wipers 2 and 33 of the servo-balance potentiometer 25 and the aligning potentiometer 3| respectively. The wiper 39 which is manually adjustable is connected by means of lead i8 to one input terminal of amplifier i3.

The vertical gyro rudder network 44 includes a vertical gyro roll operated potentiometer 45 and a roll trimmer potentiometer 46. The potentiometer 45 comprises a resistor 4'1 and a wiper 48. The resistor 41 is connected across the ends of a secondary winding 49 of a transformer having a primary winding 33. Since in the several networks to be described several secondary windings may have a common primary winding the same reference character is used to indicate in each instance the primary winding of the transformer. The wiper 46 of potentiometer 45 is driven through an operative connection 50 by a vertical ilight gyro, to be described. The potentiometer 46 comprises a resistor 5| and a wiper 52. One end of resistor 5| is connected to a center tap 53 oi resistor 4l. The other end of resistor 5| is connected to wiper 43 of potentiometer 45. The wiper 52 which may be manually adjusted as desired along resistor 5| is connected through leads 4| and 40 to wiper 33 of the aligning potentiometer 3|.

The rate gyro network 54 includes an aligning potentiometer 55, a rate gyro operated potentiometer 56 and a voltage dividing potentiometer 66. The potentiometer has a resistor 51 which is connected across the ends of a The resistor 3| is secondary winding 59 of a transformer to form two arms of a bridge. a primary winding 30. Potentiometer 55 includes a wiper 58 which may be manually adjusted over the surface of resistor 51 by a knob 60. 6| and a wiper 62. The resistor 6| is connected across the ends of secondary winding 59 to thereby form the other two arms of the bridge. A rate of turn gyro through an operative connection 63 adjusts the wiper 62 over the surface of resistor 6|. The rate gyro 65 may be of the type well known in the art which is responsive to the rate of turn of the aircraft and which upon turning of the aircraft will precess and through the operative connection 63 will position the wiper 62 in proportion to the rate of turn of the craft. The voltage dividing potentiometer includes a resistor that is connected across wipers 58 and 62. Wiper 68 0f the voltage .dividing potentiometer.. 6 6. is

The transformer has The potentiometer 56 includes a resistor 6 connected by means of lead 64 to the end or resistor 5| in network 44 that in turn is electrically connected to center tap 53.

The yaw rudder network 10 includes a yaw motor operated potentiometer 'll and a resistor 72. Potentiometer '1| includes a resistor 13 and a wiper 14. Resistor 'i3 is connected across the ends of a secondary winding l5 of a transformer to form two arms of a bridge. The secondary winding I5 is supplied by a primary winding 30. Wiper 14 may be positioned along the surface of resistor 13. Resistor l2 is connected across the ends oi the secondary winding l5 to form the opposite 'two arms of the bridge. Included in the network 'I0 is a trimmer or voltage dividing potentiometer '19. The potentiometer i9 includes a resistor 80 and a wiper 8|. One end of resistor 80 is connected to wiper 'I4 and the opposite end oi resistor is connected to a wiper 7B. Wiper 14 is electrically connected through lead 32 to wiper 62 of the rate gyro operated potentiometer 56.

Wiper 'I4 oi potentiometer is adjusted through an operative connection 83 extending from a yaw motor 84 to be described. The yaw motor 84 may be a conventional reversible type split phase capacitor induction motor. The motor 84 has terminals 55 and 86 connected to one winding and terminals 88 and 89 connected to the other winding. The terminals 65 and te are connected to the source oi alternating voltage. Terminals 88 and 89 are connected to the output terminals of an amplier 9U. 'Hue amplifier 90 has signal input terminals 9|, 93 and terminals 94, 95 which are connected to the source of alternating voltage. The yaw motor 84 and the amplifier 9@ may be similar to that disclosed in the U. S. patent to Anschutz- Kaempfe No. 1,586,233. In such amplifier and i motor combination the direction of rotation of the motor 84 depends upon the phase relationship between the voltage applied to the signal input terminals 9|, 93 of amplifier 90 and the voltage across terminals 94 and 95 of the amplifier which are connected to the source of voltage. Continuing with the elements operating the rudder network lil, the amplifier 90 may have its signal input terminals 3|, 93 connected to a yaw pickup network |00. rhe vane network |00 includes a vane operated potentiometer |0| and an aligning potentiometer |02. The potentiometer lili includes a resistor |33 and a Wiper |04 adjustable thereover. The wiper |04 is operatively driven by a vane ||2 which is rotatably carried by the aircraft so as to align itself with the direction in which the craft is moving. ends of a secondary winding |05 of a transformer having a primary winding 30. Potentiometer |02 comprises a wiper |06 and a resistor |01. The resistor |07 is connected across the ends of secondary winding |35 in parallel with resistor |03 to thus form a Wheatstone bridge. The output of the bridge is developed across the wipers |04 and |06. The wiper |56 may be manually adjusted by a knob ||3. A vane trimmer potentiometer |03 has its resistor ||0 connected across the wipers |04 and |06. The potentiometer |08 includes an adjustable tap |09 which may be manually positioned along resistor H0. One end of the voltage dividing resistor H0 is connected to ground. v

The signal input terminals Sii and 93 of ampliiier 03 may also be connected to a yaw motor reset network ||5. The network ||5 includes a Resistor |53 is connected across the Ysistor |64.

accesos 7 yaw motor operated potentiometer HB and an aligning potentiometer H1. The potentiometer ||6 includes a resistor i8 and a wiper ||9 positionable over said resistor. The resistor .H8 is connected across the ends of la secondary winding |29 of the transformer to thereby .form two arms of a bridge. The secondary winding |29 is supplied from Aa primary winding 39 of the transformer. The potentiometer i1 includes a resistor |2| and a wiper |22 manually adjusted over said resistor. The resistor y'|21 is connected across the ends of secondary winding in parallel with the resistor ||8 to thereby form the opposite two arms of the bridge.

The v'alternative connection of terminals 9|, 93 of amplifier Si? to network iil or reset network I5 is controlled by a relay |25. The relay |25 comprises an operating coil |26 and operable relay arms |21, |28. The upper arm |28 coacts with two spaced contacts |39 and |3l.

|32, |33. Coil |26 is energized from a battery through a single pole single throw yaw reset switch |36.

' Reverting to the description of the remaining l der turn control trimmer potentiometer it in- 7:'

cludes a resistor rand a Wiper |49. The resistor Piv has one end connected to wiper Ulli and has its opposite end connected to a broad center tap |155 of resistor M3. Wiper |519 ofthe trimmer potentiometer is selectively connected by means of lead |52 to the adjustable tap 8| 'of the yaw rudder bridge network 1i). The wiper |44 is adjustable through an operative connection i5# extending from a manual turn control knob |53.

The directional gyro rudder and centering bridge network itt includes a directional gyro operatedvrudder potentiometer and a centering potentiometer |62. The potentiometer |6| comprises a wiper |63 and a resistor it. The resistor |64 is connected across the ends of a secondary winding |65 of a transformer to form two arms of a Wheatstone bridge. The centering potentiometer |62 includes a resistor |66 and a A `manually adjustable wiper |61. The resistor l' is connected across the ends of secondary winding |65 in parallel with resistor ltd to constitute the other two arms of 'the Wheatstone bridge. Wiper |63 of potentiometer iti is electrically connected to one end of resistor i of the trimmer potentiometer |49. Wiper i is also operatively driven by a directional gyro llt. The directional gyro lill may be of the type disclosed in the aforesaid application and in which movement proportional to deviation of the aircraft from a desired direction about its turn axis applies a movement to wiper it relative to re- The manually `adjustable wiper |51 is connecte-d to ground. Since terminal .i6 of ampliier I3 is also connected to ground the input circuit is thereby completed.

The right rudder, as stated, is connected to `control cables 1| which extend from a cable The cable drum |12 is reversibly The l Iswitch arm |21 coacts with two spaced contacts The potentiometer id! comprises driven by a right rudder servomotor |13. The servomotor |13 is reversibly controlled by an amplifier |14. The amplier |14 has terminals |15 and |16 connected to a source of alternating voltage which may be the inverter, not shown, of the aircraft. The terminals |11 and |18 constitute the signal input terminals of amplifier |14. The input circuit connected to terminals |11 land |18 of 'amplifier |14 as previously stated includes a servo-balance and aligning network |8.

The `servo-'balance and aligning network |80 includes 'a servomotor operated potentiometer |82 and an aligning potentiometer |23. The potenti'- oineter |62 includes a 'resistor ist which is connected across the opposite ends 'of a secondary winding to form two arms of a W-he'atstone bridge and a wiper .|85 which is operatively driven from the servomotor |13. The potentiometer |83 comprises a resistor |81 which is conneeted across the Yends of secondary 'winding |85 in parallel with resistor |311 'to form the other two arms of the bridge and a manually adjustable wiper |88. The secondary winding |83 is supplied from a primary winding 30 of the transformer. The network ISB includes a right vrnd-- der ratio potentiometer iSd. The potentiometer itil consists of a resistor |9| and a wiper |92. rihe resistor isi is connected across the wipers |S5 and it to form the voltage dividing 'resistor for the output of the bridge. The manually adjustable tap EQ2 is connected to input terminal |11 of amplifier i'ifi. Wiper |88 of the aligning potentiometer |63 is electrically connected through leads l and #il to adjustable tap 52 of the trimmer potentiometer i6 of networkfli.

Since the remaining elements of the input circuit to amplifier |15 are also part of the input circuit of amplier i3 and since these elem-ents had been previously described their coaction with the servo-balance network iiiil may be considered similar to their coaction with network '22 in the input circuit to ampliiier 3.

Roll axis control Control vof the aircraft about the roll axis is obtained from two elevons. As stated previously one elevon is mounted in each wing. The left elevon, not shown, is connected to operating cables 2 extending from a cable drum '2||. AThe cable drum 2i! is driven by the left elevon servomotor 2i2. The servomotor 2|2 in turn is controlled by the left elevon servomotor ampliner 253. The ampliier servomotor arrangement is similar to that provided for the operation or" the rudders of the aircraft.

The amplifier 2 i3 has an input control vcircuit that includes active components comprising -a servo-balance and aligning network 222, a vertical gyro bank and centering bridge network 24|, a directional gyro banking network V25|. a directional gyro motorized network idd and a turn control aileron network 3135. As in the case of the rudder servomotor amplifier arrangements, the direction of rotation of the left eleven servomotor depends upon the phase relationship between the voltage across the signal input terminals 219, 22E of amplifier 2|3 and the voltage across terminals 2|8, 223 of ampliiier '2te' which are connected to a source of voltage such as an inverter, not shown, of the aircraft.

The servomotor 213 iis .electrically connectedto an amplifier 214. The servomotcr amplifier combination is similar to that provided for the operation of the left elevon. The ampliiier 214 has signal input terminals 211 and 218. Amplier 214 has additional terminals 215 and 216 which are connected to a source of alternating voltage which may be the inverter of the aircraft. As in the left eleven servomotor and amplifierarrangement, the direction of rotation of the servomotor 213 depended upon phase relationship between the voltage across the signal input terminals 211, 218 and the voltage across the terminals 215, 216. The signal input circuit includes active components comprising a servo-balance and aligning network 320, the vertical gyro banking and centering network 24|, the directional gyro banking network 25|, the directional gyro motorized network 400, and the turn `control aileron network 305.

Reverting to the input network for amplifier 2|3, the servo-balance and aligning network 222 includes a Wheatstone bridge 224. The Wheatstone bridge 224 consists of a servomotor operated potentiometer 225 and an aligning potentiometer 23|. The potentiometer 225 consists of a resistor 226 which is connected across a secondary winding 228 of a transformer, and a wiper 221 operatively driven by the servomotor 2|2. rEhe secondary winding 223 is supplied from a primary winding 39 of the transformer. The potentiom eter 23| consists of a resistor 232 connected across the ends lof secondary winding 220 in parallel to resistor 226 and a wiper 233 which may be manually positioned by knob 234. The wipers 221 :and 233 constitute the output members for the bridge 224. The network 222 includes a left eleven ratio potentiometer 231. This potentiometer consists of a resistor 238 and an adjustable tap 239. The resistor 230 is connected across the output members 221, 233 of the bridge 224. The adjustable tap 239 is connected by means of lead 22| to a signal input terminal 2| 9 of amplifier 2|3.

The vertical gyro banking and centering network 24| includes a vertical gyro roll axis operated potentiometer 242 which consists of a resistor 243' and an adjustable wiper 244 and a centering potentiometer 246 consisting of a resistor 241 and a manually adjustable wiper 248. The resistor 243 is connected across the ends of a secondary winding 245 of a transformer having a primary winding 30. rThe resistor 241 is connected across the ends Iof the secondary winding 245 in parallel with the resistor 243 and as thus connected the two potentiometers 242 and 246 constitute a Wheatstone bridge. The output members of the bridge are the wipers 244 and 248. Wiper 244. is connected by means of a lead 240 and a resistor '342 to one end of resistor 239 of potentiometer 231. The wiper 244 is operatively driven through a connection 249 by a vertical iiight gyro 250. The vertical night gyro 256 may be of the type well known in the art whose rotor is mounted for rotation a-bout a vertical axis which axis may be maintained in a vertical position during night by known suitable gravitational responsive means. The rotor also is mounted to have a rotation about two horizontal axes that are respectively perpendicular to each other and to the rotational axis of the rotor. The vertical gyr-o 250 is so mounted in the aircraft that it applies movement to Wiper 244 with respect to resistor 243 upon the aircraft tilting about its roll axis.

The directional gyro banking network 25| includes a rst directional gyro operated potentiometer 252 consisting of a resistor 253 and a wiper 254; a second directional gyro operated potentiometer 255 consisting of a resistor 256 and a wiper 251; a iixed resistor 259; a xed resistor 260; and a trimmer potentiometer consisting of a resistor 262 and an adjustable tap 263. The opposite ends 0i resistor 256 are connected to the same end of a secondary winding 266 or a transformer having a primary Winding 30. The resistor 256 has a center tap 265 which is connected through resistors 259 and 260 placed in series to the opposite end of secondary winding 266. Resistor 253 of potentiometer 252 has one end connected to wiper 251 of potentiometer 255. The Aopposite end of resistor 253 is connected to the junction between resistors 259 and 260. The resistor 262 of the bank trim potentiometer 26| is connected across the wiper 254 and a center tap 264 of resistor 253. Wipers 254 and 251 of the first and second directional gyro operated potentiometers are operatively driven through an op# erative connection 258 by the directional gyroV |'l0 in proportion to the magnitude of the deviation and the direction of the deviation of the 'craft about the vertical axis. A lead 269 extends from the adjustable tap 263 `of the trimmer potentiometer 26| to wiper 248 of the centering potentiometer 246.

The directional gyro motor operated network 400 includes a motor operated potentiometer 40| consisting of a resistor' 402 and an operable wiper 403; a resistor 405 having a center tap 406; and a trimmer potentiometer 408 having a resistor 409 and a wiper 4|0. Resistor 462 of potentiometer 40| is connected across the ends of a secondary winding 4| of a transformer having a primary winding 30. The resistor 405 is conF nected across the ends of the secondary winding 4H in parallel with the resistor 402'. The re'- sistor 409 of the trimmer potentiometer 408 is connected across the wiper 403 and the center tap 406 of resistor 405. A lead 3|6 extends from wiper 4|0 to an end of resistor 262 of potentiometer 26|. The wiper 403 of potentiometer 21| is operatively driven by a motor 234. The motoi` 284 is similar to the yaW motor 84. The motor 284 is reversibly controlled by an amplier 290 which is similar to the amplifier 30 which controls the yaw motor 64. The signal input terminals 29|, 293 of amplifier 290 corresponds with the signal input terminals 9|, 93 of ampliiier 90. The input terminals 29| and 293 are alternatively connectable with the directional gyro rudder network or the directional gyro motor operated network 400. This alternative control of the amplifier 290 by networks |60 or 400 is controlled by the lower pair of contacts |32-, |33 and switch arm |21 of relay |25 previously described. The circuit to the signal input terminals 29| and 293 of amplifier 290 is also oontrolled by a relay 300. This relay 300 consists of an actuating coil 336 and a movable arm 30| which coacts with two spaced contacts 302, 303.

Continuing with a description of the remaining component parts which form the input circuit to left eleven amplifier 2| 3, the turn control aileron network 305 comprises a turn con.- trol operated potentiometer 306 having a resistor 301 and a wiper 308, and a trimmer potentiometer 309 consisting of av resistor 3|0 and an adjustable tap 3i The resistor 301 is connected across the ends of a secondary winding 3 2 of a transformer having a primary winding 30. The resistor 3|0 of the trimmer potentiometer 309 has one end connected to a broad center il 1 `tail 3 I4 of the resistor Sill and has its other ,end .connected to wiper 3.93 of potentiometer A30S. The junction of center tap 3.14 and resistor .3 t is connected to ground. A lead 3|5 extends from wiper .3H of the trimmer potentiometer to one V.end of resistor 213 of 'potentiometer 218. The

wiper `308 is operated over ,resistor 3d? .bymeans .of an Operative connection its from a manually operable turn control lknob |53. lThe circuit to the .input terminals of amplifier 2 i3 is completed from the grounded connection `from the june tion of center tap Sid and resistor 316 to the grounded terminal .22d of amplifier 2|3.

Considering the component parts of the circuit connected to the input terminals 211 and v22113 -O the right elevon amplifier 214, the .network 32D includes Va servornotor operated :potentiometer 32| consisting of a resistor 32,2 and a wiper :323 driven -by the servomotor 213, an aligning potentiometer 32d consisting of a resistor 3,25 and f a manually ,operable wiper r326, and a right elevon ratio potentiometer 321 consisting .of a resistor bridge. VA lead extends from the adiusta-ble tap .329 to the input terminal 211 of :amplifier 214. A junction kof Wiper 323 and resistor 328 is connected through a xedresistor 34| and lead 240 to wiper 244 of the vertical .gyro banking and centering network 24 i.

The remaining components of the aileron or :roll axis signal input circuit of amplifier 1214 have .been described with reference to the input circuit vof the left elevon `amplifier 2|3 therefore Vthese components will not again be described.

Pitch axis :control Control about the pitch axis of the aircraft is provided lby the two elevons. For the purpose of affecting control -about the pitch axis the V elevons are moved in the same direction rather than Vin opposite directions as is vprovided to effeet control about the roll axis. The input circuit to amplier 2| 3 for affecting elevator operation of the left elevon consists of active com- -ponents comprising network 224 and a composite network 350.

The input control circuit for right elevon amplier 214 to effect elevator operation of the right elevon consists of active components comprising lnetwork 323 and composite network 35E.

The network 224 of the input circuit to the left elevon amplier 2f|3 has been described with reference to the aileron input circuit for that amplii'ler.

The network 35|! comprises a vertical gyro pitch axis and centering network 35|. a vertical gyro roll axis up elevator network 352 and two eoual. xed resistors 34| and 342. The network 35! comprises a vertical gvro operated potentiometer 35.3 consisting of a resistor 354 and a wiper 355, and a centering potentiometer 351 consisting of a resistor 358 and a manually adjustable wiper 359. Resistor 354 is connected across the ends of a secondary winding 330 of a transformer having a primary winding 3c. Resistor 3.58 is connected across the ends of secondary winding 360 in `parallel with resistor 35d. Thus Vit may be seen vthat potentiometers 353 and .351 are arranged in the form of a Wheatstone bridge 'with the wipers 355 and 359 constituting the ,output members of the bridge. The wiper 355 is operated by the vertical gyro 259 in response to movement of the aircraft about the pitch or lateral axis of the craft. The movements given to wiper 355 are proportional to the magnitude and direction of the movement of the aircraft about the pitch axis.

The vertical gyro up elevator network 352 ncludes a trimmer potentiometer having a resistor 32 and an adjustable tap 3&33 and a vertical gyro operated potentiometer 365 consisting -of a resistor v35E and an operable wiper 361. Resistor 352 is connected across the opposite ends of .a secondary winding 313 of .a transformer having .a primary winding 35. The two ends of resistor 333 are connected Ato one end cf resistor 352. A center tap 3H of resistor 355i is connected to wiper 353 of the trimmer potentiometer 36|. A lead 3'i2 extends from wiper 333 of the trimmer potentiometer 35| to the wiper 359 of the centering potentiometer 351. Fixed resistor 35.2 has one connected to one end of resistor 3M. The renaining end of resistor 3&2 is connected to wiper 355 of the pitch ar-:is potentiometer 353. `The remaining end of resistor 3&5 is connected to wiper 3d? of the vertical gyro roll axispotentiometer Lead is connected to the junction of resistors and Sdi. From vlead. 25rd the input control circuit of amplier 253 extends through components which are inactive with respect to elevator operation and comprise networks 24|, 25|, 213 and 3dB 'to ground.

As stated previously the input kcircuit to the right elevon amplifier 2112 providing elevator action of the right elevon consists of network 325i and network 35o. The vnetwork 32o has been previously described with respect to the input circuit of amplifier 21d for providing aileron operation of the right elevon. The network 353 has also been described with reference to the input circuit of the left elevon amplifier A2|3 for providing elevator action. These prior descriptions may be resorted to if necessary. Like the input circuit to amplifier 2 i3 controlling the left servomotor 2.!2, the remaining portion of the input circuit to amplier 21d of the right elevon servomotor 213 for providing elevator operation consists of the lead Vnetwork 25|, network 25|, network 215, network 355, to ground and to the ground terminal 218 of amplifier 2M.

Having described the control networks for the various .ampliiiers further detais of the apparatus will be described hereinafter. Associated with the manually operable turn control knob |53 is a circular cam 33t operatively connected to the turn control knob. Cam 3:39 is operatively .associated with three spaced contacts 38E, 332 and v333. A directional arm lock coil .38d has one end connected to the upper spaced Contact 382,V and the opposite end of coil .385i may be connected to ground. Coil 38d of relay 36@ has one end also connected to contact 3S! and has its opposite end connected to ground.

The middle contact 382 is connected to one end of 'battery 357 whose opposite end is connected to ground. An erection cutout coil 383 has one end connected to the lower spaced contact 333 and has Vits opposite end connected to ground. .The

13 directional arm lock coil 384 and the erection cutout coil 383 are operative components of the directional arm lock and the erection cutout mechanism disclosed in the aforesaid application 447,989.

The directional gyro |13, previously described, operates a pinion 390 vwhich is engaged with a rack having a cam member 39|. Coacting with the slidable cam member 39| is a depressi'ble contact 394 which may engage a lower contact 395. The depressible Contact 334 is connected to battery 381. The lower contact 395 is connected to the ungrounded end of coil 388.

As disclosed in the aforesaid application 447,989 the operation of the directional arm lock coil 334 prevents transmission of movement from the directional gyro I'I'Il to the elements operated thereby such as the wiper |53 of the directional gyro rudder network |53 or the pinion 333 upon operation of the turn control knob |53. In addition, the energization of the coil 338 of the erection cutout mechanism prevents the operation of the erecting means about the roll axis for the vertical tions on their resistors 2 6 and 32 there will be no potential difference between the wipers 25 and 33. There will thus be no potential drop across the rudder ratio potentiometer resistor 38. If wiper 33 be moved 4over resistor 32 to alter the relative positions of wipers 33 and 21 a potential difference will exist between the wipers 21 and 33. This potential is applied across the resistor 38. The

vadjust-able tap 3 8 of the potentiometer 31 may be adjusted along the resistor 31 to select any portion of this potential drop between wipers 21 and 33. The selected voltage drop across resistor 38 `is applied -on the one hand by means of the ad- -justable tap 33 to one input terminal I1 of amplifier I3.

In vertical -gyro roll network 44 the wiper 48 is normally at the position adjacent center tap 33. -lf wiper 48 be displaced in either direction from the center tap a voltage drop will appear across the trimmer potentiometer resistor Si. A selected portion of this voltage drop is obtained between the adjustable tap 52 and the lower end of resistor Since the adjustable tap 52 is connected to the lower end of resistor 38 of the rudder ratio potentiometer it is apparent that the selected potential drops from resistor 38 of the rudder ratio potentiometer and from resistor 5| of the trimmer potentiometer 46 are placed in series.

In the rate gyro network 54, the wiper 53 and the wiper 52 are normally at the electrical centers of their respective resistors. If wiper 58 be moved from its electrical center a voltage will be developed across wipers 58 and E2 and therefore across voltage dividing resistor S1. Wiper 63 is connected to the lower end of resistor 5| to thereby pla-ce the selected voltage output of the network 54 in series with the voltage drop selected from resistor 5 I.

In the yaw rudder bridge network 1I), wiper 14 is normally at the electrical center of resistor 13 so that the potential of wiper 14 and that of the center tap 18 of resistor 'I2 are the same. If wiper 'I4 be displaced from its electrical center a voltage appears across the wiper 'I4 and center tap 18 which is applied across the trimmer potentiometer 19. The adjustable tap 8| may be positioned along the resistor' 8|] so that a selected portion of this voltage drop will be obtained between the upper end of resistor SIB and the tap 8|. The wiper 62 from the network 54 is connected to the upper end of resistor thereby placing the selected voltage developed across resister 80 in series with that voltage obtained from the network 54.

In the rudder turn control network |40, the adjustable wiper |44 is normally at the -center tap |45 on resistor |43. If the wiper |44 be displaced from the position adjacent the center tap |45, a voltage will exist between the wiper |44 and the center tap which voltage is applied across the trimmer potentiometer resistor |50. The tap |49 may be adjusted along resistor |50 to select the desired portion of this voltage drop. Adjustable tap |49 is connected to adjustable tap 8| of the yaw rudder bridge trimmer potentiometer 19. Thus, the voltage drop from the turn control rudder network |40 as selected is applied in series with the voltage drop from the yaw rudder bridge trimmer potentiometer 19.

In the directional gyro rudder and centering network I 53 the wiper |53 and the wiper I B'I are normally at the electrical centers of their respective resistors when no potential difference exists between them. If wipers |63 and |51 are relatively displaced from the electrical centers a Voltage will exist between them. Wiper |63 is connected to one end of the resistor |50 of the turn control rudder trimmer potentiometer |42. Wiper |61 is connected to ground which is common to the ground terminal I5 of amplifier I3. The voltage developed from network I 60 therefore is in series with the voltage developed from the turn control rudder potentiometer and is in series with the voltage developed across all of the networks in the previously described input circuit of the left rudder amplifier I3. If the sum of the voltages in the input circuit of amplifier I3 is equal to zero the amplifier I3 will not operate.

With the circuit in balanced condition as shown, if the manually operable centering wiper |61 of network |69 be displaced to set up a voltage between wiper |61 and Wiper |63 the input circuit of amplifier |3 will be unbalancedV and theamplier I3 will operate. The amplifier I3 in turn will control the operation of the servomotor I2. rihe servomotor I2 operates the servobalance wiper 21 until such time as the voltage between tap 39 and the lower end of resistor 38 is equal and opposite to the voltage between wipers |63 and 61. When these voltages are equal but opposite the amplifier input circuit will be balanced and the amplifier I3 will cease operation. The servomotor too will stop adjusting the follow-up wiper 21. The operation of the servomotor to position the servo-balance wiper 21 also causes the operation of the left rudder of the aircraft. It is thus seen that the manually operable wiper |51 may be adjusted to cause the positioning of the left rudder as desired. Normally the centering wiper |61 is adjusted so that the left rudder is moved to unoperated position.

Assuming as previously described that the network I60 sets up a voltage in the input circuit l of amplifier i3 due to the'movenient of wiper 161, the amount of movement given to the wiper 2l to balance the input circuit depends upon the position of adjustable tap on the rudder ratio potentiometer resistor 38. If the adjustable tap 39 be moved toward the lower end of resistor 33, it is apparent that only a small voltage drop will be selected from the existing voltage drop across the resistor Sli, compared to the voltage that would be obtained if the tap 3S were left as illustrated. With the tap moved. toward the lower end of the resistor t8, the servomotor 2l will continue to operate the follow up wiper El until such time as the voltage drop obtained between the adjusted tap t5 and the lower end of resistor 353 balances the voltage obtained from network l. rlhe amount of movement given to the wiper 2l and thus to the left rudder will be increased when the tap :is is moved toward the lower end of resistor 3B comparedv to the movement given to wiper 2i if the tap 39 remains as shown. It is also evident that as the tap 33 is moved toward the upper end of resistor 38 that less movement of the wiper ill by the servomotor 2| will be required to set up a balancing voltage in the input circuit of ampliiier i3. By the adjustment of tap 39, it is therefore evident that the amount of movement appliesl to the left rudder for a given value of initial unbalancing voltage as obtained from the network itt may he varied as desired. The potentiometer 3l may therefore be used to vary the amount of rudder movement for a given initiating voltage and is therefore termed the rudder ratio potentiometer. TheY operation of amplier l'll for the right rudder servomotor H3 is similar to that of the amplifier I3.

`The input circuit to ampliers i3 and l'il for the left rudder and the rudder are shown in balanced condition. The amplifiers and their respective servomotors are so arranged that when the conditions are as stated and should a voltage be set up in the input circuits to the amplifiers l 3 and ile which is in phase with the voltage from the inverter one of the servomotors i2 or lil-3 will be operated the other remaining unoperative. Similarly if with the networks balanced shown and should a signal which is out of phase be set up in the input circuits of ampliiiers i3 and Elfi with the voltage .from the inverter theother servomotor will be operated to position its rudder. To apply this statement to the apparatus, assume for example that the centering wiper i6? he moved toward the left from its center position. Assume under the half cycle being considered that a positive voltage is applied across the inverter terminals I9 and 29 of an-pliiier i3 and to the terminals |75 and i'i' of ampli .er IM. Assume also that the right end of secondary winding B55 in network i is positive with respect to the lei't end. With the wiper it? as thus moved to the left the wiper H23 will be nearer the positive end of secondary H68 than wiper it? and will consequently be positive with respect to wiper i5?. This voltage being positive is in phase with the Voltage applied across the terminals ig and 2E) of amplifier i3 and that applied across terminals lit, E'i' of amplifier I'li. in its present position, the servomotor H3 will be arranged so that wiper SSE will abut a limit switch as in Figure 2 of the aforesaid application so motor l'i will not operate when an in phase signal is applied to amplier i'i. Servomotor i2 on the other hand will operate upon the application of the in phase signal when the apparatus is asarranged. The servomotor i2 will operate to move the left rudder toward open position and will also move its wiper 2'. toward the lett. Since the right end of secondary 'winding 28 like secondary winding. H55 is positive with respect to its left end the wiper 2'! will be made negative with respect to wiper 33 in network 24. The tap 39 of trimmer potentiometer 3l is therefore negative with respect to the lower end of resistor 3S. rEhus a negative potential is applied in the input circuit of ampliFier I3. When the servomotor l2 adjusts the wiper 2'.- until the negative voltage between wiper S9 and the lower end of resistor 38 is equal and opposite to the positive voltage obtained from network itt the input circuit of amplifier I3 will be in a balanced condition.

if now the wiper l5? of network 559 be moved toward the center from its leit position it is seen that the in phase signal from network it will decrease leaving a prepcnderant negative or out of phase signal in the input circuit of amplier [-3. in response to the preponderant negative or out of phase signal in its input circuit the amplifier I3 causes the servomotor i2 to rotate in an opposite direction to move the wiper 2'. toward the right from its left position. When the voltage obtained from network #Sii is balanced by the negative voltage drop across resistor 3S .between tap 3Q and the l .ver end of the resistor the amplier input cir uit is again balanced.

may be seen that until the wiper l5? of network has been moved to the electrical center ofV resistor it that the output voltage from network itt is still a positive or in phase voltage ccnsequently the servomotor H3 will remain unoperated.

es the wiper i is moved back to the center position on resistor H56, the left rudder as controlled by the amplifier i3 and servomotor l2 is moved back to normal position. At this time the input circuit of amplier i3 is again in balanced condition as shown.

`Similarly if with the apparatus as shown, the centering wiper 16'! of network 6) is moved toward the right from its center position to set up a negative or out of phase signal in the input circuits of amplifiers i3 and llt, the right servomotor |13 would position the right rudder and the left servomotor i2 due to the abutting position of its follow up wiper 2? and a limit switch, not shown, would be unoperated. By means of the arrangement provided it is apparent that only one rudder will be in an operated position or be displaced from a normal position at one time.

Having considered the operation of the rudder servomotors, the description and operation of yaw motor .fifi which drives wiper 'ifi of network l will be discussed.

The input circuit of yaw motor amplifier St is connectable with the input terminals and 3S. which as presently shown are associated with yaw network mi). If wiper ifi@ be moved toward the right from its present position it will, in the half cycle 4being considered, have a positive voltage with respect to wiper E56. The tap m9 of the trimmer potentiometer will be positive with respect to the lower end of resistor l IG which is connected to ground. Wiper tl is connected to contact l3fi of relay i' which is engaged by switch arm 128. The terminal Si is connected to switch arm t28 thus a positive or in phase voltage is applied to the input terminals of amplifier The amplifier Si? operates and causes the yew motor 34 to position wiper ld of rudder network l@ and wiper HS of reset network H5 toward the iight from their respective central positions. The ampliiier 90 will cause the servomotor 84 to operate as long as there is a potential dierence across wipers ille and |06 of the vane pickup network lili). The wiper H2 although moved to the right will become negative with respect to wiper |22 due to the phase arrangement of network H5. The wiper HS will be positioned as long as motor 2li operates.

If the single pole switch |36 now be operated to energize relay coil |26 of relay |25, the switch arm |28 is moved into engagement with contact |3i. The wiper ||9 0f network H5 is thereby connected to terminal of ampliiier 66. The grounded terminal 93 of amplifier 26 is connected through ground to wiper E22 of the reset network i |5. Avnegative or out of phase signal will thereby be applied to the amplier 92 which causes the yaw motor 62 to now rotate in a reverse direction to move wipers 14 and H9 back toward their eenter positions. The amplifier 9i] will continue to operate as long as wipers HS and 22 have a diierence of potential and while the single pole switch 35 is closed. The wiper 'ifi of the network 'lil is thus returned to its center position by the motor under the control of the reset network |'5 and amplifier 96.

Considering the input circuit for the left elevon amplier 2|3 it is believed that from the description of the function of the component parts in the input circuit of rudder ampliiier I3 that it is apparent how a voltage drop may be derived between adjustable tap 239 and the lower end of resistor 238 of network 222. The vertical gyro banking network 24| is similar to the network |60 in the rudder input circuit of ampliiier !3 and its manner of supplying voltages is also clear.

The network 225i is an arrangement whereby two potentiometers have their wipers adjusted concurrently from the directional gyro. The voltage between wiper 251 and center tap 265 depends upon the magnitude of the movement given to wiper 251 but is independent of the direction of movement. This voltage between the wiper 251 and center tap 265 is applied across the resistor 253. The voltage between wiper 252 and center tap 262 also depends upon the magnitude or the signal from the directional gyro |16 but its phase depends also upon the direction of movement. Since the voltage between wiper 224 and center tap depends upon the displacement of wiper 25d with respect to the center tap 264 and also depends upon the voltage applied across the resistor 25@ it is apparent that the voltage between the wiper 252 and center tap 264 varies as a non--inear function of the displacement or deviation obtained from directional gyro i'i. This voltage between wiper 2213 and center tap 262 varies in phase and magnitude with the direction and amount of deviation and it is applied :across resistor A desired portion thereof is selected between wiper 263 and the lower end of resistor 262.

The motorized directional gyro network 286 is :similar to network 222 therefore it is clear how a potential may be obtained between wiper H2 and the left of resistor 52.

The turn control aileron network 365 is a simple vpotentiometer arrangement with a voltage divider ar to that in network oi the input circuit ci. rudder ainpiiiier i 3. The selected voltage drop from the turn control aileron network 325 is obtained between wiper Si! and the lower end of resistor 3 i2 which is connected to ground.

It is thus seen how the voltage drops or voltages from networks .222, 212i, 251i., 212 and 325 are com 18 nected in series and constitute the input circuit components to amplifier 2|3. Similarly the input circuit to amplier 214 for the right elevon to provide aileron control is obtained by substituting the network 32S for the network 222 for the left elevon amplier 2|3.

The servomotors 2|2 and 213 that operate the leit elevon and the right elevon respectively are so arranged that when signals of the same phase are applied to their respective amplifiers 23 and 212 the servomotors 2 i2 and 213 rotate in opposite directions. For example, ir the centering knob is operated to move the wiper 2l|8 to the left, the wiper 244 will be positive with respect to the wiper 248 in the half cycle under consideration. This positive or in phase signal will be applied equally to the amplifier 2i3 and to the amplifier 214. This in phase signal will cause the servomotor amplier 2|3 to operate and cause the left elevon servomotor 2|2 to raise the left elevon. The servomotor 2|2 will adjust the servo-balance wiper '221' to the left to set up a balancing voltage in the input circuit of ampliner 2i3.

rihe right elevon amplifier 21d in response to the positive or in phase signal will cause the servomotor 213 to lower the right elevon and to move wiper 323 toward the left end of resistor 322. The wiper 323 will be adjusted until the input circuit to ampliiier 214 is in balanced condition.

As the wiper 228 is moved back to the center position the decrease in the positive signal in the input circuit of ampliiier 233 results in a negative unbalanced signal in that input control circuit consequently the ampliiier 213 causes the servomotor 212 to rotate in the reverse direction. In the same manner the ampliiier 214 responds to the preponderance of the negative signal and its input control circuit and causes the servomotor 213 to rotate in the reverse direction raising the previously lowered right elevon and moves the wiper 323 toward the center position. If wiper 248 be moved toward the right from its center position the operation of the servomotors 2 2 and 213 will be the reverse of that described previously.

With respect to the signal input circuit of amplifiers 2i3 and 21d for providing elevator operation the function of the network 33| in obtaining a voltage output is similar to that oi the vertical gyro banking network 24| in the aileron input circuit.

The vertical gyro up elevator network 352 is unlike any of the previous networks. In network 352 the two ends of resistor 366 are connected to the same end of secondary winding 310. The center tap 31| of resistor 366 is connected to the adjustable tap of resistor 362. age between the movable wiper 361 and the center tap 31| will not vary in phase as it is displaced from one side of center tap 31| to the other side of center tap 31| but will remain of the same phase. between wiper 361 and center tap 31| varies with the amount of movement of the wiper 361 and also with the adjustment given to tap 363 on resistor 362. The output of network 352 is obtained between wiper 361 and wiper 363 and does not change in phase in a particular half cycle irrespective of the direction of movements of wiper 361. The output of network 352 is in series with the output of network 35|.

It was stated with respect to the ampliiier input circuits to ampliers 2|3, 214 that for signals of like phase the servomotors 2|2, and 213 The voltf The magnitude of the voltage would be operated in opposite directions. It is apparent, that the servomotors 2|2 and 213 will rotate in the same direction for opposite signals to provide elevator operation of the elevons. The resistors 342 and 34| are connected across the network 350 in order to provide opposite phased signals to amplifiers -2|3 and 214 as the result of an initiating signal appearing in networks 35| or 352. For example, if the wiper 359 of network 35| be moved to the left it will be negative with respect Vto wiper 355 in the half cycle under consideration. This difference of potential will be applied from wiper 355 to the left end of resistor 342 and from wiper 358 through network 352 to the right end of resistor 34|. The circuit is thus completed through the resistors 342 and 34|. The potential of the left end of resistor 342 is higher than the right end of 342. Similarly, the left end of resistor 34| will be positive with respect to the right end of resistor 34|. The junction of the resistors 342 and 34| is connected to ground through the aileron input circuit. The potential of the left end of resistor 342 is applied to amplifier 2|3 and the potential of the right end of resistor 34| is applied to the input terminal 211 of amplier 214. A positive or in phase voltage signal will therefore be applied to amplifier 2|3 whereas a negative or out of phase signal will be applied to amplier 214. By the means thus described opposite phase signals are supplied to the ampliiiers 2|3 and 214 to provide elevator operation of the elevons when a signal voltage is developed in either network 35| or 352.

Operation The operation of the system may be considered when the aircraft is simply in a yawed position but that the longitudinal and pitch axes are level. The various amplifier input circuits are considered to be in a balanced condition. The single throw switch |33 is in open position with the switch arm |28 of relay |25 engaging spaced contact |30. The turn control knob |53 is in normal unoperated position at which time the relay coil 386 of relay 300 is unenergized. The switch arm 30| of relay 300 is therefore in contact with spaced contact 302.

Assuming the plane is yawed to the right. By this is meant it is headed to the right from the actual direction in which it is moving. In such condition of yaw, the vane l2 rotates in a counterclockwise direction to align itself with the direction in which the aircraft is moving. This counterclockwise rotation of vane ||2 rotates the wiper |04 whereby it is moved toward the right end of resistor |03 Vof network |00. It is assumed with respect to every network except network ||5 that the right end of the respective secondary windings are positive with respect to the left end in the particular half cycle under consideration. In network ||5 the secondary is phased so that the right end thereof is negative with respect to the left end under the half cycle being considered. With wiper |04 moved toward the right the adjustable tap |09 on the trimmer potentiometer |08 is positive with respect to ground. A positive or in phase signal is applied to amplifier 90 from tap |09 through the previously described circuit to amplifier 50. The amplier 90 causes the yaw motor 84 to rotate and position wipersr14 and H9 toward the right. The yaw rudder bridge will develop a positive or in phase voltage signal which appears across the upper end of resistor 80 and adjusta- 20 ble tap 8|. ampliers 3 and |14. It was stated previously that when a positive signal is applied to the ampliier |3 and |14 that only the servomotor l2 will operate. The servomotor |2 positions the left rudder toward open position and at the same time operates its follow up wiper 21 to balance the input circuit to amplifier I3.

ItV may be noted that the yaw motor 84 will rotate as long as the aircraft is in a yawed condition.

Under the applied left rudder the aircraft tends to turn toward the left about the vertical axis. The rate gyro responds to the turning oi the aircraft toward the left and moves wiper 62 toward the right thereby impressing a negative signal on the input circuit of the amplifiers. Similarly the directional gyro responding to the tendency to change heading toward the left from the desired heading moves its wiper |63 toward the left thereby impressing an additional negative signal on the input control circuit of the amplifiers.

As the aircraft tends to change heading toward the left which is sensed by the directional gyro |10 the directional gyro not only moves wiper |63 of network |60 but also positions the wipers 254 and 25'! in the aileron directional gyro network 25|. The wipers 254 and 251 are moved toward the left to thereby impress a negative voltage which is present between the adjustable tap 263 and the lower end of resistor 262 on the input circuit of the elevon amplifiers 2|3 and 214.

The directional gyro rudder network |30 at this time also imposes a negative signal on the input terminals 29|, 293 of amplifier 290'. The amplier 230 causes its motor 284 to rotate to move wiper 213 of network 210 toward the left. The network 210 therefore impresses a negative signal upon the input circuits to amplifiers 2|3 and 214.

In response to the negative voltage signal in their input circuits the amplifiers 213 and 214 operate their respective servomotors 2 l 2 and 223. In response to the negative signal the ampliiier 2| 3 causes its servomotor 2|2 to lower the left elevon while the amplifier 214 causes its servomotor 13 to raise the right elevon. The appli cation of such elevon action causes the plane to bank toward the right.

In response to the bank toward the right or tilt to the right about its roll axis the vertical gyro 250 responds to such tilt. Since the planes movement is about its roll axis the wiper 244 in the vertical gyro bank network 24| is moved toward the right. The wiper 361 in the vertical gyro up elevator network 352 is also moved toward the right. rlhe wiper 43 in the vertical gyro rudder network 44 is moved toward the right.

The movement of wiper 244 toward the right in the vertical gyro banking network 24| causes the amplifiers 2|3 and 214 to operate whereby the left elevon is raised toward its normal position and the right elevon is lowered toward its normal position.

The movement of wiper 321 toward the right in the up elevator network 352 causes a negative signal to be applied to amplifier 214 and a positive signal to be applied to the input circuit oi amplifier 2|3. In response to the negative signal the servomotor 213 raises the right elevon. In response to the plus or positive signal the amplier 2|3 causes the servomotor 2|2 tc raise the left eleven. Thus it may be seen that upon movement The positive signal is applied to bothy of the plane about the roll axis an up elevator action is applied to the elevon.

In the rudder network, the signal input circuit during the time the craft is off its desired heading is supplied with a negative signal from the directional gyro rudder ietwork |50, the signal from the yaw rudder bridge network l, a signal from the rate gyro network and a positive signal from the vertical gyro rudder network As the plane approaches the desired heading after attaining a maximum deviation the rate gyro network 55 supplies a positive signal to the input circuit of ampliers i 3 and lili. 'Ihe resulting signal from network lll is such as to cause the aircraft to fly in what is known as a coordinated turn. In a coordinated turn, the aircraft is neither skidding nor slipping or is not in a yawed attitude.

As the plane approaches the desired heading, the directional gyro Elfi moves the wiper i633 of the directional gvro rudder network i553 toward the right also moves the wipers and 25? in the directional gyro aileron network 25d toward the right due to the decrease in the amount of deviation from the desired heading.

In the aileron input circuits to amplifiers 213 and 2l@ the movement of the wipers 255e 25? toward the right decreases the value of the negative signal on these ampliners which in eifect leaves a preponderant positive or in phase signal in their input circuits. In response to the positive signal from the aileron network the amplifier 2l3 causes the servomotor 2i2 to raise the left elevon. rIhe amplifier Elli on the other causes the right elevon servornotor 21'3 to lower the right elevon. Such movement of the right and left elevon causes the bank angles to the right to be decreased.

In response to the decrease in the bank angle or tilt to the right the vertical gyro moves lwiper 2M: of network 26S toward the left. rThe gvro 25e also moves the wiper Bill of network 552 toward the leit and a wiper 128 or" the vertical gyro rudder network del toward the left.

rlhe signal obtained from the vertical gyro banking potentiometer 25E at this time causes the elevons to be moved back toward center position. In the network the movement of the wiper 3E? toward the lett causes the elevons to be moved from an up elevator position back toward normal position.

The movement of wiper lil in the vertical gyro rudder network 136i toward the left decreases the positive signal from this network. It had been stated that while the aircraft was in a right turn that the vane i12 controlled the 'network lt to provide a positioning of either rudder so that the aircraft would ily without yaw. As long as the junction. of leads il!! and teit is positive with respect to ground the servornotor l'i3 will not be operated by amplifier iM. If the left rudder had been positioned while the aircraft was in the right turn in order to prevent the craft from becoming yawed, the movement of wiper 48 toward the left would in eilect decrease the positive voltage operating on the input circuit with ampliners i3 and H3. The junction of leads fill and ISA with the leit rudder operated is positive with respect to ground therefore the decrease in the positive signal in effect is negative signal or an unbalanceable negative voltage on amplifier i3 which causes the servoniotor l2 to move the left rudder toward closed position. Thus the movement of wiper lil toward the left due to the decreased bank results in the junction of leads 40 and |94 becoming negative with respect to ground consequently the amplifier |13 causes the servomotor V54 to operate the right rudder after the left rudder has been moved to closed position.

The operation during the time that the deviation is decreasing is continuous. In this continuous operation the directional gyro through the directional gyro aileron network 25! tends to decrease the bank of the aircraft by raising the left elevon and lowering the right eleven. The vertical gyro 25e in response causes the vertical gyro banking,- network 25d to return the eleven toward normal.

With respect to the elevator action of the elevons the decrease in the banking angle causes the wiper Btl to be moved toward zero position and eventually causes any elevator operation of the eleven to be removed.

In the rudder networks as the deviation angle decreases and wiper les is moved toward the center position it reduces the negative Voltage applied to the input circuits of ampliers I3 and H. If the amplifier Ile had caused the servomotor illu' to operate the right rudder in response to the negative potential of the junction or" leads 46 and ld in respect to ground, the decrease in the negative signal reduces the negative potenm tial of this junction with respect to ground. The positive signal on amplifier |14 obtained from the voltage drop between adjustable tap ISE of the ratio potentiometer with respect to the lower end of resistor iQI would exceed the negative voltage in the input circuit. The amplifier H74 would cause the servomotor |13 to operate and cause the right rudder to be moved toward the closed position.

es the aircraft reaches its desired heading, the wiper 153 of the directional gyro potentiometer and the wipers 2er and 25'! of the directional gvro aileron potentiometer are at their center positions. The vertical gyro 25B has also moved the wipers 2id, 35i' and 4S back to their normal positions. The plane is now headed in its desired direction with the plane in level horizontal position. The yaw responsive vane H2 will have through motor d have adjusted the network l@ to provide any signal required to position the left or right rudder to remove the yaw condition of the aircraft.

If the aircraft had been yawed to the left at which time it was moving in a direction which was clockwise from its heading a similar operation would be provided to correct the plane for the yawed condition and to return it to its desired direction of flight.

The operation of the system in stabilized control to automatically compensate for unsymrnetrical power will now be considered. We may assume that the plane is of the multi-engine type and that the power of a motor in the right side of the aircraft has decreased from its normal value. This sudden decrease in power of the motor on the right wing over that in the left wing causes the aircraft to veer to the right. The right wing, also due to the decrease in the velocity of the air over the wing, loses some of its effective lift and the right wing begins to drop.

As during any change in heading in automatic stabilization, the directional gyro senses the change in heading of the aircraft and displaces wiper 1&3 of the directional gyro rudder network ISE. The rate gyro 55 also responds to the turning action of the plane about the turn axis. Wiper |63 is moved to the right or the center of resistor |65 in network |69 and wiper 62 of rate 23 network e is moved to the left of the center of resistor 6i. The networks 'ISG and Eli therefore supply a positive signal to the amplifier circuits for ampliers i3, Vid. The robalancing networks 22 and Se are assumed to be in balanced position and the servomotors i2 and H3 are in normal position. Therefore with the positive pulse or signal applied to the control circuits of the amplifiers i3, ile, only servomotor l2 will operate to open the lett rudder to check the veering cf the craft to the right. i

To provide a signal which anticipates the dropping of the right wing and applies a corrective effect, the directional gyro I'i in addition to positioning wiper l63 of network It@ positions wipers 255i, 257 of directional gyro aileron network Zei to the right. The signal from directional gyro rudder network Iil is also applied to the amplier 25253 which through motor 28d positions wiper it of aileron network im?. rEhe wiper i 3 is moved to the right and is therefore positive with respect to the center tap of resistor 85. The signal supplied to the aileron control network for ampliers 2i3, 2id by network positive in character, similarly the wipers Zia-'J being moved to the right a positive signal is derived from aileron network which is applied to the aileron control circuits for amplifiers ZES, 2M. The preponderant positive signal causes the amplifier 2 i3 to operate its servomotor 212 to raise the left elevon. The aznpliiier 2M in response to the preponderant positive signal causes the servomotor 2'5'3 to lower the right elevon to increase the lift on the right wing to oiset its tendency to drop. The rebalancing wiper 22? of network 224 is moved to the left to balance the control circuit for its amplifier M3. The rebalancing wiper 23 of network 322 is moved to the left by servomotor 213 to balance the control circuit for its amplier 2M.

In the aileron channels the signals from aileron networks #it and 25i in applying a positive signal to the control circuits for amplifiers ZES, 2M had caused the raising of the left elevon and the lowering of the right elevon. The plane now tilts toward the left to regain its desired heading.

The tilting of the plane to the left causes vertical iiight gyro 255 to position the wiper 251i in roll axis aileron network 213i, the wiper i323 in the rudder compensating network 4M, and the wiper in the up elevator compensating network 352.

The signal from network 352 due to the displacement of wiper 357i causes the application of up elevon to each of the elevons. The manner in which this is obtained was previously described.

The wiper 2id of the aileron network 2LH beinc moved to the left the network 243i supplies a n.- atlve control signal to the circuit for controllii g amplifiers 2 i3, 2id. The negative signal causes the amplier 2l3 to eiect movement of its servo 2li to lower its operated left elevon. The negative signal on amplifier 2M causes it to opera-te and effect rotation of servornotor 273 whereby the lowered right elevon is raised towards normal position.

rhe aileron network 21S which is in the control circuits for amplifiers 213, 2M is increasing the positive value of the control signal applied to such circuits.

The positioning of wiper 43 of the vertical gyro rudder network to the left by the vertical flight gyro 25E causes a negative signal to be developed across wiper 52 and the lower end of resistor Si. lThis negative signal causes the servomotor l2 to be operated to position the left rudder toward unoperated position.

As the aircraft approaches the desired heading, the directional gyro ile moves wiper it toward the leit from its right position on resistor il. The rudder network 15! decreases the Value of its positive output signal therefore the circuit controlling amplifier i3 has a preponderant negative signal. Such signal causes :the amplifiers i3 and i to operate servomotors l2 and H3 in sequence. They move the rebalancing wipers 2'! and it toward the right from their leftward positions. At the same time the operated left rudder is moved toward the closed position and the right rudder is opened. Due to the eiiect in the amount of the operated rudder the turning or" the aircraft toward its desired heading decreases in rate and therefore the rate gyro signal of rate network 5S decreases. The wiper 32 which had assumed a right position due to the left turning toward desire-:l heading now moves from its right position toward the center oi resistor Si. The rate gyro signal from network as the plane moves toward its desired heading sets up a decreasing negative signal opposing that provided 'oy network i555. The rate gyro signal being decreasingly negative in character` and being opposed to the positive signal from network iti! tends to cause the ampliner H3 to effect rotation of its motor il?, such direction as to move the operated richt rudder toward closed position. Should the aircraft be steadied on its heading when such heading is fin-ally reached the directional gyro will have moved its wiper back to the center resistor 56e and the rate gyro signal from network 5 will be Zero with the wiper 5a at the center o1" resistor 57. The servomotor i il will have moved wiper 85 t its extreme left position and the right rudder will have been placed in normal closed position.

As the desired heading is approached, the directional gyro moves wipers 256i and 25's' to the left from their right positions. This decreases the positive signal from network rc2 and causes an unha-lance or preponderantly negative signal in the aileron circuits for controlling ampliers ZES, Zit. The negative signal causes the amplier i to operate to eiect rotation of servomotor 252 whereby the left elevon is lowered. At the same time the negative signal on amplier 251i causes it to effect rotation or" servomotor M3 whereby the right elevon is raised. The aircraft under this lowered left elevon and raised right elevon tends to lessen its angular position about the roll axis.

The vertical night gyro 35@ responds to the lessening in the angular position of the aircraft and moves wiper 2de toward the right from its left position, moves wiper @el toward the center tap Sii, and moves wiper i5 toward the left or toward the center or" resistor 13's. Movement of wiper 2M toward the right from its left position decreases the value ci the negative signal output from network -ii and the control circuits for the aileron control of amp-liners 2id, 2-'Ll becomes preponderantly positive. The ampliner EES in response to the positive signal from the aileron circuit tends to raise the left elevon from its previously lowered position. Similarly the amplier 2id in response to the positive signal from the aileron circuit causes the servomotor gt3 to lower the previously raised right elevon.

In the elevator control circuits for the ampliers Zi, Zli, the decrease in the signal from network 352 causes the amplifier' it to have a preponderantly negative signal which causes it to lower its left elevon. At the same time the decrease in the positive output of network 352 results in a decreased voltage drop across resistor 34|. The decrease in the voltage drop across resistor 34| decreases the value of the negative signal derived from this resistor and in effect increases the positive voltage on amplifier 214. The amplifier 2li responds to the positive signal and lowers its right elevon through servomotor 213. The amount of up elevon which had been previously applied is thereby decreased as the aircraft approaches the desired heading. When the aircraft ultimately reaches the desired heading the vertical flight gyro 253 will have moved the wiper 331 back to center tap 31| in network 352.

The movement of wiper 48 of network 64 from its left position toward center tap 53 due to the movement of vertical gyro 256 in response to the lessening of the angular position of the aircraft about the roll axis decreases the negative signal derived from network 44. The control circuit for amplifier |14 is therefore unbalanced in a positive direction. The amplifier |14 operates and through the servomotor |13 moves the right rudder tow-ard unoperated position. At the same time the servomotor |13 moves wiper i255 toward the left hand side of resistor` |84.

When the aircraft reaches the desired heading, the directional gyro will have moved wiper |33 of network |53 back to the center of resistor |54. Directional gyro |10 will also have moved wipers 254, 251 of network 25| back to the centers of their resistors 253 and 25B.

Under these conditions, the impedance network 21t provides the only source of control voltage for operating the ampliers 2 I 3, 214 to obtain aileron action. The wiper 213 of network 21e is not returned to the center of resistor 212 since it is displaced all during the time that the aircraft is in deviation and at a rate proportional to the magnitude of the deviation. The signal obtained from network 216 is positive in character and would therefore cause the amplier 2 I 3 to operate servomotor 2I2 to effect the raising of the left elevon whereas the amplier 214 is operated by a positive signal in its control circuit to cause the servomotor 213 to lower the right elevon. When the aircraft is in the desired heading; therefore, the right elevon is in lowered position and the left elevon is in a raised position. The lowering of the right elevon tends to increase the angle of incidence of the right wing and to give it increased lift whereby the tendency of the right wing to drop due to the decrease in the speed of an engine mounted in the right wing is offset.

lis previously explained the circuit for effecting elevator action of the elevons has been balanced due to the fact that wiper 361 has been returned to center tap 31| as the aircraft approaches the desired heading. Therefore, the elevons will not retain their operated positions to apply elevator action when the aircraft is cn desired heading.

In the rudder control circuits for the ampliiiers the impedance network |60 is in balanced condition when the craft is on the desired heading. Although the craft is at this time in a level position fore and aft and laterally, due to the displaced ailerons, yet due to the unsymmetrical power applied to the plane it will still have a tendency to turn toward the right. The tendency of the craft to turn to the right while it is in level position may cause it to skid. A turn without a bank tends to cause the aircraft to skid, and therefore it is not headed in the direction in which it is moving. However, the vane 2 responds to the skidding or yawed condition of the aircraft. The vane ||2 moves wiper |04 to the right from its center position on resistor |03. This movement unbalances network |00 and operates amplifier Si?. Amplifier 9o on operation causes the motor 84 to position wiper 14 of network l toward the right. The wiper 14 will be positive with respect to center tap 18 and the upper end of resistor will be positive with respect to the wiper 8|. A positive signal is therefore imposed on the control circuits for amplifiers i3, |13. If the networks 2D, 2U are in balanced condition, the positive pulse or signal causes the amplier I3 to operate. The amplier I3 causes the servomotor |2 to operate the left rudder. The servomotor |13 does not operate since in normal position it does not respond to a positive signal on amplifier |14.

The directional gyro iii! will respond also to any skidding action which tends to change the heading of the aircraft from that desired and it moves wiper |63 to the right whereby wiper |63 is positive with respect to wiper |61 and network |33. The positive signal from network |63 also causes the amplifier I3 to effect movement of the left rudder to check the tendency of the aircraft to change its heading. The application of left rudder therefore causes the aircraft to head in the desired direction.

When the aircraft is headed in the desired direction the directional gyro |10 will have moved wiper |33 back to the center of resistor |64 and no signal is obtained from network |63. However, the wiper 14 of network 10 will retain its displacement to the right despite the fact that the aircraft is not in yaw. The displacement of wiper 14 to the right of its center on resistor 13 causes a positive signal to be placed on the control circuits of amplifiers i3, |14. The amplifier I3 through its servornotor I2 causes a permanent displacement or positioning of the left rudder to correct for any tendency of the aircraft to yaw.

By the above means should unsymmetrical power develop in the aircraft it is compensated by a permanent displacement of the elevons in which one is moved to a raised position and the other one is moved to a lowered position to compensate for the tendency of the wing to drop which has suffered the loss of power. At the same time a rudder is permanently displaced to correct for any tendency of the aircraft to yaw or to change its heading due to the unsymmetrical power.

If the unsymmetrical power exists with less power in the motors arranged in the left wing, the operation is similar whereby the aircraft is restored to its original heading with compensating aileron positioning of the elevon and a permanent displacement of the rudder to correct for the tendency of the craft to yaw.

Tum control If the pilot wishes to manually effect the turn of the aircraft to the right, the knob |53 is rotated to the right thereby displacing wiper Ili of network |4 to the left and wiper 3&3 of the aileron turn control network 335i to the left. Wiper |44 will therefore be negative with respect to the center tap |45 of resistor |43 consequently wiper |49 of the rudder trim potentiometer |42 will be negative with respect to ground. A negative signal is therefore applied to ampliers i3, |14. Amplifier |14 responds to the negative signal, causes motor |13 to move the right rudder 2'? into operated position and rebalancing wiper |85 to balance thev input circuit.

Also wiper 38B is negative with respect to the `center tap 3M of resistor 3Q? and consequently wiper 3H of the aileron trim potentiometer 333 isV negative with respect to ground. The aileron control circuit for ampliers 213, 2M, receives a negative signal. The amplifier 2l3 responds to the negative signal and causes its servomotor 2|2 to lower the left elevon; the amplifier 2id responds to the negative signal and causes its servomotor 273 to raise the right elevon. The servomotors adjust the rebalancing wipers 22?, 323.

The plane now is placed in a right bank due to the positioning of the elevons and' the rudder through the operation of the turn control knob. The vertical gyro 25% responds to the roll movement of the plane and moves wiper 24e towards the right and wiper i8 of the compensating network iti to the right. The movement of wiper 263 in the aileron network 2li! towards the right applies a positive signal to amplifiers 2i3, 2id. In response to this positive signal, the servomotor 2i2 raises the left elevon and servomotor 273 lowers the right elevon with the consequent movement of wipers 223, 323. The positive signal in network i6 due to the movement of wiper 138 to the right applies the positive signal to am- 4 plilier l'il which causes servomotor H3 to move the right rudder toward closed position and moves rebalancing wiper H35.

The plane turns in its banked position until the desired heading is reached at which time the manual -control knob 53 is moved back to zero position thereby moving wiper SLM and wiper 338 to their center positions. A positive signal is now applied to the rudder network causing the amplifiers H4 and I3 to effect rotation of servomotors H3 and l2 in sequence to close the right rudder and open the left rudder.

The positive signal in the aileron control network causes the motor 2 i 2 to raise the left elevon and motor 213 to lower the right elevon. The application of the opposite elevon causes the right wing to raise, in other words the right tilt of the plane is decreased.

The vertical iiight gyro 250 responds to the decreasing in the tilt about the roll axis and moves wiper 2M toward the left from its right position and moves wiper te in the network iii toward the left from its right position.

The aileron control circuit receives in eiect a negative signal causing servomotor 2 I2 to lower the left elevon and servomotor 2`i'3 to raise the right elevon. Similarly the negative voltage signal in the rudder networks causes the servomotor l2 to move the left rudder to the closed position.

At this time the craft is on the desired heading with the networks balanced and the elevons and rudders in normal position.

The vertical flight gyro also moves wiper 36? in network 352 of the elevator control network to apply up elevator to the elevons while the plane is turning and also centers the elevons as the plane is steadied on the desired heading.

The operation of the turn control knob 53 also rotates cam 383 whereby contacts 38S, 332, and 333y are brought into engagement. The closing of these contacts energizes the erection eut-out coil 388, the directional arm lock coil 28 385, and relay operating coil 38a for the purposes previously explained.

Resetting operation It is evident that the wiper le of the yaw rudder network 13 and the wiper 213 of the network 210 may have been displaced from their normal position. In order to reset or return these wipers to the center position of their respective resistors, the single pole switch |35:` may be closed. The amplifier 93 is thereby placed under control of yaw reset network H3 which would have had its wiper HS displaced with wiper iii. The amplifier 33 causes the motor 8d to return wipers 1f/l and H3 to their normal position.

The closing of switch i causes switch arm i2? of relay 25 to engage lower contact 133 thereby placing amplifier 29S under the control of network lie whereby it causes the motor 284 to return the wiper iBS to normal position. The function of relay Stii may become evident at this time. If the reset switch i3d were closed while the turn control knob E33 were operated from normal position the amplifier 230 would receive a signal not only from network 93 but also from network 335. Under these circumstances the wiper i333 would not be brought back to its center position by motor 2M. In order to prevent such return to other than a zero or normal position the relay Se@ disassociates the network figli from amplifier 233 while the turn control knob 53 is operated.

It is now evident that I have provided ight control apparatus which normally stabilizes the aircraft and which will correct the flight of the aircraft for conditions of yaw. This apparatus will also correct for permanent mistrim of the air-craft due to differences in power supplied from engines on opposite sides of the longitudinal axis.

Having described the preferred embodiment of my invention, but realizing that changes in the particular details described may be made without departing from the spirit of my invention, I do not wish to confine my invention to the specific structure described.

What is claimed as new is:

1. Flight control apparatus for an aircraft having means for positioning the aircraft about an axis to control the headingA thereof, said apparatus comprising; actuating means for said positioning means; control means for said actuating means including a direction maintaining means responsive to deviations in heading of said aircraft and wind operated means responsive to the angular difference between the longitudinal axis of said aircraft and its direction of movement relative to the air, said difference responsive means being arranged to provide a control effect in said control means which increases with the magnitude of said difference and duration of said difference, said control effect remaining after removal of said difference whereby its control effect overrides that provided by said deviation responsive means.

2. Flight control apparatus for an aircraft having a control surface for positioning said aircraft about an axis, said apparatus comprising; control surface power ineens; control means for said power means; and a balanceable operating means for said control means including a control device responsive to the extent of deviation of the aircraft about said axis, a follow up second control device operated by said power means, means responsive to the magnitude of the angular difference between the heading of the aircraft and the direction of the relative air, a third control device operated in accordance with the duration and magnitude of said angular difference whereby movement of said follow up second control device renders said first and third control devices ineffective without further movement to control said control means.

3. Flight control apparatus for an aircraft having means for positioning said aircraft about two axes, actuating means for said positioning means; control means for said actuating means, one control means including means responsive to deviations of the aircraft about one axis and means responsive to the difference in heading of said aircraft from its direction of movement, said difference responsive means providing a signal which overrides said deviation signal and another control means including means responsive to said deviations of the aircraft about said one axis whereby aircraft is turned about one axis until it is headed in the direction in which it is moving and whereby it is moved about another axis and caused to head in a desired direction.

4. Flight control apparatus for an aircraft having plural means for positioning said aircraft about its turn and roll axes; actuating means for each said positioning means; control means for each said actuating means, one control means including a controller responsive to the deviations in heading of the aircraft, a means responsive to the yawed condition of the aircraft, an operative means responsive to the yaw responsive means, and a yaw controller moved by said operative means in accordance with the duration and inagnitude of yaw whereby said two controllers operate said control means; and another control means includingI a controller responsive to the deviations in heading of the aircraft.

5. Flight control apparatus for an aircraft having means for positioning said aircraft about an axis, said apparatus comprising; power means for said positioning means; control means for said power means including signal deriving and signal combining means; means for actuating a first signal deriving means in response to the duration and magnitude of yaw of said aircraft including operative means for positioning said signal deriving means, for peratinga second deriving means concurrently with said first signal means and means for controlling said operative means by said second signal means for returning said both signal deriving means to unoperated position.

6. Flight control apparatus for an aircraft having means for positioning said aircraft about an axis; actuating means for said positioning means; control means for said actuating means including a variable impedance adjusted in accordance with a yawed condition of the aircraft, relative air direction responsive means for adjusting said impedance, an operative means controlled by said impedance, and a controller connected to said operative cans and moved in accordance with the magnitude and duration of the yawed condition of the aircraft; and means for disassociating said operative means from said impedance and for returning said controller to nonoperated position.

7. Flight control appaartus for an aircraft having means for positioning said aircraft about an axis; actuating means for said positioning means;

control means for said actuating means, a network for operating said control means comprising a first Variable impedance adjusted in accordance with the deviations of the aircraft about said axis, means responsive to the yawed condition of said aircraft, operating means controlled by said yaw responsive means, a second and a third variable impedance controlled by said operating means, a fourth impedance connected across the second impedance, connections from said first impedance to said control means and to said fourth impedance and from said fourth impedance to said control means; and connections from said third impedance to said operating means including means for rendering said yaw responsive means ineffective tc control said operating means and rendering said third impedance effective to control said operating means whereby said operating means varies said second and third variable impedances.

8. In flight control apparatus for an air raft having means for positioning said aircraft about one axis; actuating means for said positioning means; control means for said actuating means; means for operating said control means comprising; a first source of voltage varied in accordance with the deviations of the aircraft about said axis, means responsive to the yawed condition. of said aircraft, operative means controlled by yaw responsive means, a second and a third source of variable voltage con'trolled by said operat've means, a variable impedance connected across the second source of voltage, connections from said first source to said control means and to said variable impedance, a connection from said variable impedance to said control means; connections from said third source of voltage to said operative means including means to render said yaw responsive means ineffective with respect to said operative means and to render said third source effective to control said operative means whereby said operative means reduces the value of the voltage from said second and third sources of voltage.

9. Control apparatus for a dirigible craft having control surfaces for positioning said craft about two axes; power means for said control surfaces; control means for each said power means, a control means for one power means including a controller responsive to the duration and magnitude of yaw of the craft and a second controller responsive to the deviation of the craft about one axis and a control means for the other power means including a controller responsive to the magnitude of the deviation of the craft about the said one axis and another controller responsive to the magnitude and duration of the deviation about the said one axis whereby one power means is operated to turn the craft about said one axis to remove the yaw of the craft and the other power means is operated to turn the craft about another axis to cause said deviation to be removed.

l0. Flight control apparatus for an aircraft having means for positioning said aircraft about two axes, said apparatus comprising; actuating means for said positioning means; control means for each actuating means, one control means including a controller responsive to the yawed condition of said aircraft and said other control means including a controller responsive to the magnitude of the deviation of the aircraft about one axis and a second controller responsive to the magnitude and duration of the deviations of the aircraft about said axis, said deviation 3l controller being actuated by movement of the aircraft about said one axis resulting from the operation of the yaw condition controlled positioning means.

1l. Control apparatus for a craft having control surface means for positioning said craft about its roll axis, said apparatus comprising; power means for said positioning means; control means for said power means including a balanceable network, said network including a rst means having a variable impedance adjusted in accordance with the deviations of the craft about its vertical axis, a second means having a variable impedance adjusted in accordance with the magnitude and duration of the deviations of the craft about said vertical axis said impedance remaining adjusted on removal of said deviations, a third means having a variable impedance adjusted in accordance with the position of the craft about said roll axis, and a follow up or rebalancing variable impedance adjustedv by said power means whereby upon tendency of said craft to continue in deviation about the verticaliaxis the second adjusted impedance efects operation of said control means and displacement of said. control suri'ace to re.- move said deviations.

l2. Control apparatus for an aircraft having positioning means for. controlling the position of the aircraft about an axis, said apparatus comprising; actuating means said positioning means; control means for said actuating means; means for operating said control means including a first variable impedance, a second variable impedance, a third variable impedance electrically connected across output members of said second impedance, motor operated means for adjusting said second impedance, and a fourth variable impedance controlling said motor means, electrical connections from said first impedance to said control means, from said first impedance to saidthird impedance, from said third impedance to said control means, and electrical connections from said 'third impedance to said motor means including. switch means to render said fourth impedance ineffective to control said.

motor means and for rendering said third impedance ecctive to control said motor means;` and additional switch means for rendering said third :dance ineffective to control said motor inc-ans upon adjustment of variable` impedance.

13. Flight control apparatus for an aircraftY impedance controlled by one power means, andY another operating means comprising a signal combining circuit including a variable source of signal voltage including means responsive to the deviation of the aircraft about said vertical axis, a variable source of signal voltage including means responsive to the magnitude and duration of the deviation of the aircraft about .saidl 32 vertical axis, and a rebalancing source of voltage controlled by the other power means.

14. Flight control apparatus for an aircraft having a rudder for controlling the heading of the aircraft, said apparatus comprising: rudder power means, control signal combining means including iirst and second adjustable signal controllers for controlling said power means, means responsive to the magnitude of deviation in heading of the craft for adjusting said first controller, wind controlled means responsive to the magnitude of the difference between the heading of said aircraft and its direction of movement relative to the surrounding air, and motor means controlled by said difference responsive means for adjusting said second controller by an amount dependent upon the magnitude and duration of said difference, a third controller positioned with said second controller, and switch means between said third controller and said wind controlled means on the one hand and the motor means on the other whereby said third controller may be connected to said motor means to return said second and third conl trollers to a normal position.

l5. Control apparatus for an aircraft having control surfaces for controlling the aircraft about two axes, said apparatus comprising: power means for operating said control surfaces; a control means for each power means; means for operating each control means including a plurality of signal generating means and means for combining generated signals; attitude means responsive to movement thereof about one axis and actuating a signal generator in each operating means; course responsive means for actuating a signal generator in each operating means; and means responsive to yaw of the aircraft to actu.- ate a signal generator in one operating means;

and manually operable means for actuating a signal generator in each operating means and for rendering said course responsive means ineifective to actuate its signal generators in both operating means.

16. Control apparatus for an aircraft having a control surface for controlling the aircraft about its roll axis, said apparatus comprising: control surface power means, control means for said power means, operating means for said control means including a plurality of signal generators and means for combining generated signals; means responsive to change of heading of said aircraft for actuating a signal generator in proportion to the magnitude of said change; means for actuating a second signal generator from said heading change responsive means in proportion to the magnitude and duration of deviation, said second signal generator remaining actuated upon removal of said change in heading; and means for actuating a third signal generator from said power means.

17. Control apparatus for an aircraft having control surfaces for controlling the aircraftv about two axes, said apparatus comprising: power means for operating said control surfaces; a control means for each power means; means for operating each control means including a plurality of signal generating means and means for combining generated signals; means responsive to change in heading of the craft for actuating a signal generating means in each operating means; means responsive to yaw of the craft and actuating a signal. generator in one operating means in accordance with a time function of the conditionof yaw, means operated by said heading` responsive means for actuating a signal generator in the other operating means in accordance with a time function of change of heading, and means responsive to change in attitude of said craft for actuating a signal generator in each operating means.

18. Flight control apparatus for an aircraft having means for positioning the aircraft about an axis, said apparatus comprising: power means for said positioning means; and balanceable electrical control means for said power means including voltage generating means responsive to the diierence between the heading of the aircraft and its direction of movement, operative means responsive to said difference responsive means and operated thereby at a rate proportional to said difference, a voltage generating controller 34 positioned by said operative means in accordance with the duration and rate of movement of said operative means and a follow up voltage generating controller positioned by said power means.

ROBERT J. KUTZLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,485,781 Ferdon Mar. 4, 1924 1,958,258 Alexanderson May 8, 1934 2,280,117 Crane et a1 Apr. 21, 1942 2,343,288 Fink Mar. '7, 1944 2,420,932 Cornelius May 20, 1947 2,463,585 Young Mar. 8, 1949 

